The judgment, signed Tuesday by Judge William Smith of the U.S. District Court for the District of Rhode Island, overturns an April jury verdict that slapped Microsoft with the largest patent award on record.

“We are pleased that the court has vacated the jury verdict and entered judgment in favor of Microsoft,” spokesman Kevin Kutz said Tuesday.

The case has spanned six years and numerous courts. Irvine, Calif.-based Uniloc USA, and its Singapore-based parent company, filed the lawsuit in Rhode Island in September 2003, alleging Microsoft used its patented technology for software activation.

Download the judge’s order, in which he explains the case and gives his reasoning for reversing the jury’s verdict (PDF)

The technology in question included the use of a software activation key to keep users from installing licensed software on more than one computer. Uniloc initially sought $560 million in damages and said Microsoft deployed the technology in Windows XP and Office.

In October 2007, the Rhode Island court ruled in Microsoft’s favor. Uniloc appealed to the U.S. District Court for the Federal Circuit, and in 2008 the Federal Circuit affirmed the lower court’s ruling but required it to re-examine part of the case.

In April 2009, a jury found that Microsoft willfully infringed Uniloc’s patent (No. 5,490,216). The ruling required Microsoft to pay a patent-law record $388 million in damages to Uniloc, and attracted international media attention.

Tuesday’s judgment upended that ruling.

In a statement, Uniloc CEO Brad Davis said the company plans to appeal again.

“We are disappointed by the decision the trial judge has made to overturn the jury’s unanimous verdict in Uniloc’s patent infringement case against Microsoft,” Davis said in a statement sent to seattlepi.com. “We believe that the jury’s verdict in April was thoughtful, well reasoned and supported by the evidence presented. Since the patent status remains unchanged, Uniloc will continue to protect its intellectual property and appeal the Judge’s decision to override the jury’s verdict to the US Court of Appeals. We are confident that Uniloc will ultimately prevail.”